Dual-mode colorimetric/photothermal lateral flow immunoassay using Au-Pt-CdS Hetero-Nanostructure for highly sensitive detection of progesterone in food samples.

Progesterone (P4) residues, whether resulting from improper veterinary application or environmental persistence, are established endocrine disruptors within the food supply chain. This underscores the need for analytical methods that are both sensitive and dependable. In response, we constructed a lateral flow immunoassay (LFIA) with dual-signal output, utilizing colorimetric changes and photothermal effects for the quantitative determination of P4. The assay employs Au-Pt-CdS hetero-nanostructures as versatile signal-enhancing probes. The Au-Pt-CdS nanohybrids exhibit strong and broad optical absorption spanning the visible to near-infrared (VIS-NIR) region, coupled with a high photothermal conversion efficiency of 45.60%, which collectively amplifies the signal in both detection channels. After optimization, the limits of detection (LODs) for the colorimetric/photothermal dual-mode LFIA were measured to be 0.352 ng mL-1 and 0.087 ng mL-1, respectively. These values represent sensitivity improvements of 1.7-fold and 6.9-fold over conventional LFIA systems based on gold nanoparticles (AuNPs). The developed method showed strong resilience to matrix interference in fortified milk and pork samples, with recovery rates between 81.49% and 123.06% and reproducible results (RSD <10%). Consequently, this dual-mode approach provides a robust, rapid, and user-friendly platform suitable for the on-site monitoring of steroid hormone residues in food systems with intricate composition.